If the combustion conditions vary from one cylinder to another, it will show up in how the plugs look, like if one cylinder is burning oil or water...
Does it ever got hot?
White smelly smoke is usually burning coolant.
If you have a crack in the block that affects compression and is leaking, then I would think that is the answer right there.
Pull the plug wire off #6 (I'm assuming) and see if the smoke disappears??
Most shop manuals have pictures in them of what different things look like on a spark plug.
I'd start looking for a new engine...
